Natural SUSY On Trial: Status of Higgsino Searches at ATLAS Julia - - PowerPoint PPT Presentation

Julia Gonski

Harvard University

25 October 2018 US LHC User’s Association Annual Meeting

Natural SUSY On Trial:

Status of Higgsino Searches at ATLAS

• J. Gonski

25 October 2018

• Provides unification of forces,

dark matter candidate, and solution to hierarchy problem

• Higgs mass quadratic corrections

cancelled by new supersymmetric partners; higgsinos, stops and gluinos especially influential

➡ What do we search for first?

SUSY (The Defendant)

2

• J. Gonski

25 October 2018

SUSY Mass Spectrum

(if we got to pick)

˜ H

˜ tL

˜ bL

˜ tR

˜ g

˜ W

˜ B

˜ Li, ˜ ei

˜ bR

˜ Q1,2, ˜ u1,2, ˜ d1,2

3

mass

• Naturalness = reduce fine

tuning ⟹ 10%

• Dark matter candidate!

Dominantly (but not purely) higgsino

• Lightest three higgsinos are

compressed (Δm ~ few GeV)

• J. Gonski

25 October 2018

SUSY Mass Spectrum

(if we got to pick)

˜ H

˜ tL

˜ bL

˜ tR

˜ g

˜ W

˜ B

˜ Li, ˜ ei

˜ bR

˜ Q1,2, ˜ u1,2, ˜ d1,2

4

weak scale (< 400 GeV)

mass

H)(

~

W)(

~

B)(

~

Gauginos

~

흌20~ 흌1± ~ 흌10

~

흌30 ~ 흌40 ~ 흌2±

Mass Eigenstates

• Naturalness = reduce fine

tuning ⟹ 10%

• Dark matter candidate!

Dominantly (but not purely) higgsino

• Lightest three higgsinos are

compressed (Δm ~ few GeV)

• J. Gonski

25 October 2018

SUSY Mass Spectrum

(if we got to pick)

˜ H

˜ tL

˜ bL

˜ tR

˜ g

˜ W

˜ B

˜ Li, ˜ ei

˜ bR

˜ Q1,2, ˜ u1,2, ˜ d1,2

5

mass

weak scale (< 400 GeV)

• Naturalness = reduce fine

tuning ⟹ 10%

• Dark matter candidate!

Dominantly (but not purely) higgsino

• Lightest three higgsinos are

compressed (Δm ~ few GeV)

˜ χ 0

4 ˜

χ 0

3 ˜

χ 0

2 ˜

χ 0

1

˜ χ±

2 ˜

χ±

1

˜ B ˜ W ˜ H

• J. Gonski

25 October 2018

SUSY Mass Spectrum

(if we got to pick)

˜ H

˜ tL

˜ bL

˜ tR

˜ g

˜ W

˜ B

˜ Li, ˜ ei

˜ bR

˜ Q1,2, ˜ u1,2, ˜ d1,2

6

mass

weak scale (< 400 GeV)

• Naturalness = reduce fine

tuning ⟹ 10%

• Dark matter candidate!

Dominantly (but not purely) higgsino

• Lightest three higgsinos are

compressed (Δm ~ few GeV)

˜ χ 0

4 ˜

χ 0

3 ˜

χ 0

2 ˜

χ 0

1

˜ χ±

2 ˜

χ±

1

˜ B ˜ W ˜ H

• J. Gonski

25 October 2018

SUSY Mass Spectrum

(if we got to pick)

˜ H

˜ tL

˜ bL

˜ tR

˜ g

˜ W

˜ B

˜ Li, ˜ ei

˜ bR

˜ Q1,2, ˜ u1,2, ˜ d1,2

7

mass

weak scale (< 400 GeV)

˜ χ 0

4 ˜

χ 0

3 ˜

χ 0

2 ˜

χ 0

1

˜ χ±

2 ˜

χ±

1

˜ B ˜ W ˜ H

• Naturalness = reduce fine

tuning ⟹ 10%

• Dark matter candidate!

Dominantly (but not purely) higgsino

• Lightest three ewkinos are

compressed (Δm ~ few GeV)

• J. Gonski

25 October 2018

Higgsino Searches at ATLAS

8

˜ ±

1

˜

2

W Z p p ˜

1

q q ˜

1

` ` j

* *

• Final state: 2
• pposite sign same

flavor soft leptons

• Challenging!
• Low production

cross section

• Small Δm → low

MET, very soft leptons

• J. Gonski

25 October 2018

˜ ±

1

˜

2

W Z p p ˜

1

q q ˜

1

` ` j

• Final state: 2
• pposite sign same

flavor soft leptons

• Challenging!
• Low production

cross section

• Small Δm → low

ETmiss, very soft leptons

Higgsino Searches at ATLAS

* *

9

• J. Gonski

25 October 2018

˜ ±

1

˜

2

W Z p p ˜

1

q q ˜

1

` ` j

• Final state: 2
• pposite sign same

flavor soft leptons

• Challenging!
• Low production

cross section

• Small Δm → low

ETmiss, very soft leptons

Higgsino Searches at ATLAS

* *

10

ISR kick = ETmiss trigger

Low mll ~ Δm

• J. Gonski

25 October 2018

Current Exclusion

11

[1] ATLASSummaryPlots [1]

• J. Gonski

25 October 2018

Current Exclusion

12

LEP2

[1] ATLASSummaryPlots [1]

• J. Gonski

25 October 2018

Current Exclusion

2L compressed

13

[1] ATLASSummaryPlots [1]

• J. Gonski

25 October 2018

Current Exclusion

Disappearing track

14

Pure higgsino/wino state: Δm~100 MeV ⇒ long lifetime ~10-11s

[1] ATLASSummaryPlots

m~100 MeV ⇒

[2] ATL-PHYS-PUB-2017-19 [1] [2]

• J. Gonski

25 October 2018

Current Exclusion

15

Relic density disfavors pure higgsino LSP! (Well-Tempered Neutralino)

[1] ATLASSummaryPlots [1] [3] [3] arXiv:0601041

• J. Gonski

25 October 2018

Areas of Improvement

16

New working point gives us muons down to 3 GeV (2019)

[1] ATLASSummaryPlots [1]

• J. Gonski

25 October 2018

Areas of Improvement

17

New working point gives us muons down to 3 GeV (2019) More luminosity

[1] ATLASSummaryPlots [1]

• J. Gonski

25 October 2018

What’s Next?

200 400

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• Natural SUSY is still well-motivated! (& experimental constraints are

weakest in the electroweak sector)

• Fine tuning < 10% possible for m( ) < 2.5 TeV and m( ) < 1.5 TeV
• Next analysis: 1L + track, softer leptons, HL-LHC! (2026+)

˜ g

˜ t

• J. Gonski

25 October 2018

200 400

19

˜ g

˜ t

What’s Next?

• Natural SUSY is still well-motivated! (& experimental constraints are

weakest in the electroweak sector)

• Fine tuning < 10% possible for m( ) < 2.5 TeV and m( ) < 1.5 TeV [4]
• Next analysis: 1L + track, softer leptons, HL-LHC! (2026+)

[4] arXiv:1611.05873

• J. Gonski

25 October 2018

200 400

?

20

• Natural SUSY is still well-motivated! (& experimental constraints are

weakest in the electroweak sector)

• Fine tuning < 10% possible for m( ) < 2.5 TeV and m( ) < 1.5 TeV [4]
• Up next: softer leptons, 1L + track, HL-LHC! (2026+)

˜ g

˜ t

What’s Next?

[4] arXiv:1611.05873

• J. Gonski

25 October 2018

Backup

21

• J. Gonski

25 October 2018

Precision Corrections to Fine Tuning

22

Buckley, Monteux, Shih arXiv:1611.05873

Λ= Λ=

≤ 10

∆ ≡ 2δm2

H

m2

h

m2

H = m2 H,bare + ∆m2 − ∆m2

Δm2 = |μ|2

(at tree level)

μ ≤ 400GeV

• J. Gonski

25 October 2018

Why Quasi-Degenerate?

Wino/bino as lightest electroweakino, # light states is different!

• one neutral state for a light bino;
• one neutral and one charged state for a light wino.

Depends on neutrino mass matrix in MSSM! Using

is is M ˜

N 0 =

B B @ M1 mW tθW cβ mW tθW sβ M2 mW cβ mW sβ mW tθW cβ mW cβ µ mW tθW sβ mW sβ µ 1 C C A study we will take M1 ( e B0, f W 0, ψ0

d, ψ0 u) basis

M ˜

C =

✓ M2 p 2sβmW p 2cβmW µ ◆ ⇥ ⇤ f ⇥ ⇤ µ, the splittings between the mostly Higgsino states are

• mχ±

1

• mχ0

1

• ⇡ m2

W (1 ⌥ s2β)

2(M2 + |µ|)

• mχ0

2

• mχ±

1

• ⇡ m2

W (1 ± s2β)

2(M2 |µ|) ,

• mχ0

2

• mχ0

1

• ⇡ m2

W (±|µ| s2β + M2)

(M 2

2 |µ|2)

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arXiv:1401.1235

• J. Gonski

25 October 2018

But we haven’t found anything yet!

The Stop

Limits up-to ~1 TeV in stop mass … but no limits if m(LSP) ≳ 400 GeV

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1500

• J. Gonski

25 October 2018

The Gluino

25

But we haven’t found anything yet!

2500

• J. Gonski

25 October 2018

ATLAS SUSY Summary

26

• J. Gonski

25 October 2018

2L Higgsino Search

• Met > 200 GeV → trigger
• pT(jet1)>200 GeV → ISR
• |힓흓(jet,Met)| > 1.0 → mis-measured Met
• nJet(50 GeV)=1,2 → no jets expected from the signal
• bJet veto → ttbar background
• upper cut on lepton pT → soft leptons in the final state;
• upper cut on mll → small invariant masses expected;
• Met/Ht → good discrimination as seen in the Run-2 analysis;
• m휏휏 → Z휏휏 background;

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• J. Gonski

25 October 2018

Making ETmiss with ISR

• With no other final state objects, LSPs are back to back, no ETmiss in event
• Require ISR jet: collimate LSPs, generate measurable ETmiss for trigger

pTLSP1 = 100 GeV pTLSP2 = 100 GeV pTLSP1 = 100 GeV pTLSP2 = 100 GeV Total ETmiss = 0 GeV Total ETmiss = 200 GeV

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